Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$189.48	12.154%	$212.5094	$212.51	$212.50	$212.50
Purchase #2	$124.69	7.514%	$134.0592	$134.06	$134.05	$134.10
Purchase #3	$200.91	4.448%	$209.8465	$209.85	$209.85	$209.80
Purchase #4	$80.34	3.213%	$82.9213	$82.92	$82.90	$82.90
Purchase #5	$151.85	8.423%	$164.6403	$164.64	$164.65	$164.60
Purchase #6	$46.45	4.626%	$48.5988	$48.60	$48.60	$48.60
Purchase #7	$213.33	13.868%	$242.9146	$242.91	$242.90	$242.90
7 purchase totals =	$1,007.05		$1,095.4901	$1,095.49	$1,095.45	$1,095.40